How to Make Yellowed Plastic Appliances White Again

Using hydrogen peroxide.
Apply a generous amount of hydrogen peroxide (40 volume) to the yellowed plastic area using a brush or cloth. Be sure to spread the product evenly over the entire surface.

3. Place plastic wrap on top
After applying the peroxide, cover the area with plastic wrap. This allows the peroxide to stay in contact with the plastic and prevents it from evaporating too quickly.

4. Be in the sun
Place the device in the sun, if you can. Sunlight allows the hydrogen peroxide to work more effectively, making teeth whiter faster. Leave the object in the sun for about an hour.

Remove the plastic wrap and clean.
After an hour, remove the plastic wrap and clean off any excess peroxide with a damp cloth. Continue the same process as necessary until you achieve the desired result.

Other tips
Repeat: If the yellowing is severe, you may need to repeat the process several times.
Test the hydrogen peroxide on a small area first to make sure it doesn’t cause any negative reactions before using it on the entire surface.
Extra protection: To prevent yellowing, keep devices out of direct sunlight and consider using covers to protect them. DIY options
If you can’t get your hands on 40-volume hydrogen peroxide, you can use homemade options to bleach yellowed plastic from devices.